
xfconf-query -c xfwm4 -p /general/sync_to_vblank

when that setting is set(~ true)
then the system is like locked up, inside virtualbox
probably because there's no vsync to time to, so it waits forever

enable vsync:
xfconf-query -c xfwm4 -p /general/sync_to_vblank -s true
disable vsync aka sync to vblank:
xfconf-query -c xfwm4 -p /general/sync_to_vblank -s false

but you can only run these in X or with a $DISPLAY

to be able to disable it, note that you can't switch to text console ('cause host will trap ctrl+alt+f1) so must boot into text mode by adding GRUB param before boot (key e):
systemd.unit=multi-user
this doesn't seem to be working on manjaro, maybe works on arch
src: https://wiki.archlinux.org/index.php/kernel_parameters
or
systemd.unit=multi-user

just get to this xml file:
/home/emacs/.config/xfce4/xfconf/xfce-perchannel-xml/
vim xfwm4.conf
set that sync_to_vblank property from true to false

and there, fixed!

